Leaking Skylight: Why It Happens and What to Do

Skylight on roof

Skylights are meant to let in extra light, not water! Added natural sunlight makes your home feel brighter and more spacious, but leaking skylights can take all that beauty away and replace it with rotting structures or mold if you don’t catch them in time. So, if you have leaking skylights, read on to find out why they leak and what to do.

Reasons for Leaking Skylights

If you notice a small amount of water leaking out of your skylights, there are several simple ways to troubleshoot and potentially repair the leak.

1. Double check to make sure that the skylight is fully closed. Obvious but worth a try.

2. Verify that the leak is not actually pooled condensation on the underside of the glass. This happens often -- in very cold climates, in humid rooms, and with single-glazed skylights. To reduce condensation, add insulation between the framing members and the skylight itself. The easiest solution is expanding spray foam..

3. Look at the area around the skylight from both inside and outside (using proper safety precautions) to check for damp or stained surfaces.

4. Clear away any leaves, twigs, and dirt that have gathered on the skylight and check the glass itself for cracks. Seal skylight cracks with a layer of clear silicone along the entire length.

Inspect the Roofing and Flashing Around a Leaking Skylight

Once you’re sure the water is penetrating from the roof outside, look carefully to see if the shingles and flashing around the skylight are properly installed and functional. Roofing should be firmly nailed down, so repair any lifted shingles.

Next, take a look at the flashing. Because the purpose of flashing is to make a watertight seal between the skylight and the roof, any visible defects or damage (like corrosion or pinholes) are signs your flashing needs to be replaced. You should also check that the roofing material extends all the way around the flashing, including each side and the top. If there is space between the roofing and flashing, water can get trapped and cause leaks.

Seal Flashing Around a Leaking Skylight

Start by clearing any water or debris that has collected between the roofing and flashing. Then lift the roof shingles away from the edges of the skylight so you can access the flashing. Use a putty knife to add a layer of roofing cement in the gap between the edge of the flashing and the roofing. This will provide a seal against future leaks, as long as it doesn’t dry out or become brittle. Check the roofing cement sealant every few months. If it's peeling or dried out, remove and apply a new layer.

When the flashing itself is damaged or moldy, it must be replaced.

If these DIY repairs don’t do the job or if you are uncomfortable hanging around on your roof long enough to find out, then find a reliable roofing contractor near you. Certified roofers will be able to repair your leaking skylight quickly and efficiently.

Updated January 9, 2018.

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